Gargantuavis
Gargantuavis is a genus of extinct avialan stem-birds containing the single species Gargantuavis philoinos.1 G. philoinos lived during the late Cretaceous period in what is now southern France and northern Spain. Its fossils were discovered in several formations, which has been dated between 73.5 and 71.5 million years old.23 Gargantuavis is the largest known bird of the Mesozoic. The few known bones suggests a size between the cassowary and the ostrich. A study based on the circumference of the femur gives a mass of 140 kg (310 lb) like modern ostriches.1 Given its mass Gargantuavis was probably flightless. Its femur shows that it was a graviportal form rather than a cursorial bird.4 Many aspects of its biology are unknown including its diet (the skull has not yet been found). The ecological niche of Gargantuavis in its ecosystem is also mysterious because it coexisted with large predators like abelisaurids theropods. In any case, and contrary to older assumptions, Gargantuavis shows that the extinction of non-avian dinosaurs was not a necessary condition for the emergence of giant terrestrial birds. It is possible that some of the fossil eggs found in the region, usually attributed to non-avialan dinosaurs, actually belong to this bird. Discovery The first Gargantuavis fossil was found in 1995 in Var, southeastern France. This first specimen, a fragmentary set of pelvic vertebrae (synsacrum), was uncovered near the village of Fox-Amphoux in a paleontological excavation. This specimen has been described in a short note without taxonomic assignation.6 Several other specimens were later found further west, near the villages of Villespassans, Cruzy, and Campagne-sur-Aude, providing enough fossil material to describe and name the species in 1998. The species name G. philoinos, meaning "wine lover", was chosen because several of these first Gargantuavis bones were found in and around vineyards and wineries.1 The Genus name refers to Gargantua, the giant main character of a 16th-century French novel by Francois Rabelais. Gargantuavis specimens are known from five different fossil localities in Europe: The Bastide-Neuve locality, near Fox-Amphoux (Var), yielded the initial specimen reported in 1995, two other partial pelvic fragments (BN 758 and BN 763) described in 2015, and a possible rib fragment found in association with BN 763.7 The Bellevue locality, near Campagne-sur-Aude (Aude), yielded another partial pelvis (MDE C3-525), which was deemed the holotype in the 1998 description of the genus.1 This site has been dated to the early Maastrichtian, about 71.5 million years ago.8 The Combebelle locality, near Villespassans (Hérault), yielded a large femur lacking the distal end (MDE A-08), which was referred to the genus in its initial 1998 description.1 The Montplo-Nord locality, near Cruzy (Hérault), yielded a single neck vertebra (MC-MN 478) which was referred to the genus in 2013.9 A synsacrum fragment (MC-MN 1165) and an incomplete left illium (MC-MN 431), both described in 2016, were also found at this locality.3 More recently, this site has also yielded a complete femur of 23 cm, belonging to an individual of about 50 kg (110 lb).10 A quarry near the village of Laño in northern Spain (Condado de Treviño) yielded a partial syncranum (MCNA 2538) described in 2017, the only specimen known outside of France.11 This locality has been dated to the late Campanian age of the late Cretaceous, about 72 to 73.5 million years ago. Description Though Gargantuavis is only known from a few isolated fossil bones, some information about its life appearance and ecology have been inferred by studying their details. Gargantuavis is known from several specimens representing a few limited parts of the skeleton: synsacra (the fused vertebrae above the hip),6 illia (hip bones), at least one cervical vertebra,9 and two femora (upper leg bone), which was referred to the species based on the fact that it seems to fit well with the hip.110 Other than its large size, the most unusual feature of Gargantuavis was its pelvis. The pelvis of Gargantuavis was originally reported to be extremely wide, like that of a moa, though a better preserved specimen described in 2015 showed that this interpretation was due to crushing in the original. The hips of Gargantuavis, while still broad, were narrower and more bird-like than originally thought.7 In addition to their unusual width, which prevented the two ilia from meeting at the front of the pelvis, the acetabulum, or hip socket, of Gargantuavis was set close to the front, rather than closer to the middle of the pelvis.7 Some researchers have suggested that Gargantuavis was not a stem-bird at all, but rather a giant pterosaur.13 However, when this idea was tested by studying the form and internal structure of the bones, its identity as an avialan was supported.4 The avian nature of Gargantuavis was also confirmed by bone histology showing typical bird features. Paleoecology Category:Cretaceous birds Category:Prehistoric birds of Europe Category:Flightless birds Category:Basal Ornithurae